Abrading machine

ABSTRACT

The oscillatory movement of the abrasive belt of an abrading machine is detected by a pneumatic sensor and controlled by a pneumatic system. Disturbance of the operation of said machine due to abrasive dust deposited in the pneumatic system is prevented due to a motor chamber of a pneumatic motor communicating with a compressed-air source through a choke of a regulator and with an air exhaust that is alternately closed and opened by a sensor-actuated flap of the regulator.

United States Patent van der Linden 1 Aug. 26, 1975 ABRADING MACHINE inventor: Jacob Arie van der Linden.

Wuustwezel, Belgium Assignee: Maschinenfabriek A. van der Linden, Goes, Netherlands Filed: Dec. 18, 1973 Appl. No; 425,928

Foreign Application Priority Data Dec. 18, 1972 Netherlands 7217234 US. Cl 51/135 BT; 51/138 Int. Cl B24b 21/00; B24b 21/18 Field of Search 51/135 R, 135 BT, 138

References Cited UNITED STATES PATENTS Hcrcik 51/135 BT 2,587,603 3/1952 Czamccki 51/135 BT 2,597,256 5/1952 Murray 51/135 BT 3,008,276 11/1961 Kile 51/135 BT 3,504,458 4/1970 Rutt 51/135 BT Primary Examiner-Othell M. Simpson Attorney, Agent, or FrrmStewart and Kolasch, Ltd.

[ 5 7 ABSTRACT The oscillatory movement of the abrasive belt of an abrading machine is detected by a pneumatic sensor and controlled by a pneumatic system. Disturbance of the operation of said machine due to abrasive dust deposited in the pneumatic system is prevented due to a motor chamber of a pneumatic motor communicating with a compressed-air source through a choke of a regulator and with an air exhaust that is alternately closed and opened by a sensor-actuated flap of the regulator.

5 Claims, 6 Drawing Figures ABRADING MACHINE The invention relates to an abrading machine at least comprising a frame, a guide table connected with said frame for guiding work pieces to be abrased, a pressing member for pressing an endless abrading belt against the work pieces, a reversing roller rotatably journalled in an auxiliary frame which is adapted to turn relative to said frame about a pivotal axis transverse of the rotary axis of the reversing roller and which is coupled by means of a pneumatic motor for performing an oscilla tory swinging motion about the pivotal axis with the frame, a pneumatic sensor for detecting the presence or absence of the edge of the abrading belt and a sensor-controlled regulating device for controlling the pneumatic motor which comprises, at least one motor chamber communicating through the regulating device with a source of compressed air and with an air exhaust.

Abrading machines of the kind set forth are known.

The regulating device of the known abrading machine comprises a slide which establishes an alternate communication between each motor chamber of the pneumatic motor and the source of compressed air and the air exhaust. With this abrading machine disturbances are frequent, because dust, for example, abrasive dust, is deposited from the compressed air in the regulator and thus inhibits the swinging motion of the auxiliary frame. As a result, the abrading belt runs off the reversing roller and thus expensive abrading belt is destroyed, while the abrading machine and the work pieces may be also damaged.

The invention provides an improvement in the abrading machine in this respect by establishing a communication between the chamber of the pneumatic motor and the compressed-air source through a choke of the regulator and an air exhaust which is alternately closed and opened by a flap of the regulator actuated by the sensor. The regulator of this abrading machine does not include components which are relatively displaceable with a narrow fit. Also, the choke is not likely to become clogged by dust because it is continuously cleaned by the vigourous air stream required for energizing the pneumatic motor.

A symmetrical drive of the auxiliary frame is obtained by providing the regulator with a communication with a compressed-air source having two branches, each of which communicates through a choke with one of the two chambers of the pneumatic motor and which are alternately closed and opened respectively by a sensor-actuated flap.

When at least one of the chambers of the pneumatic motor comprises a spring and when the stroke of the neumatic motor is adjustable by means of a pressureincluded in the compressed-air supply duct, the stroke of the oscillatory movement of the abrasive belt can be adjusted a greater or lesser extent as the work pieces require a zigzag abrasion pattern, by increasing or decreasing the effective pressure of the air supply.

In order to enable the pneumatic motor engage the auxiliary frame without producing shocks, that is to say, without producing play producing shocks. the pneumatic motor is preferably arranged parallel to the reversing roller, the motor engaging a vertical pin connected with the auxiliary frame through a coupling element adapted to turn about a vertical pivotal axis.

tially broken away in the direction of the arrow III in FIG. 2,

FIG. 4 is a sectional view taken on the line IV-IV in FIG. 3,

FIG. 5 shows, on an enlarged scale and schematically inter-engaging components of the abrading machine of FIG. 1, the components being shown in sectional views and FIG. 6 illustrates a variant of the regulator of the pneumatic motor of an abrading machine in accordance with the invention.

The abrading machine shown in FIGS. 1 and 5 comprises a frame 1, a vertically displaceable guide table 2, connected with said frame for guiding work pieces 3 to be abraded on their bottom sides. The guide table is adapted to slide by bearing blocks 4 in vertical guides 5. During the vertical displacement of the guide table 2 vertical screw spindles 6 screwed into the bearing blocks 4 are driven in common. On the top side the work pieces 3 are guided by means of guide means 85, which are vertically adjustable independent of each other with respect to the frame 1 by means of nuts 86 and screw-threaded rods 87 for controlling the thickness of the layer to be ground off. If necessary, the guide table 2 may be urged upwards by any spring system until the work piece disposed thereon comes into contact with the guide means 85. The guide table 2 is provided with an endless conveyor belt 7, driven in the direction of the arrow 8. The abrading machine furthermore comprises a pressing member 9, which, serves to press the endless abrading belt 10 against work pieces 3, and which in the embodiment shown, includes a rubber-clad roller 12- rotatably journalled in the frame 1 and driven in the direction of the arrow 11 or it may be formed, as an alternative, by a metal shoe (not shown) coated with a smooth sliding cover, for example, graphite tissue and arranged in between rollers guiding the abrading belt and arranged at a slightly higher level. A reversing roller 15 is rotatably journalled in an auxiliary frame 16, which is pivotally journalled about a piston rod 18 of a pneumatic cylinder 19, the vertical center line 17 of which traverses of the rotary axis 16 of the reversing roller. When energized, the pneumatic cylinder 19 urges the auxiliary frame 13 upwards, the abrading belt 10 being thus stretched. For replacing the abrading belt 10 with a different one, the lower side of the cylinder 19 is evacuated and a supporting block 21 is removed. After replacement of the abrading belt 10 the supporting block 21 is reset in place and fixed by a bolt 22 between the upper frame 1a and the bottom frame 117, the chamber 20 being reenergized by compressed air.

In operation the abrading belt 10 reciprocates in the directions of the arrows 23. In order to maintain control of these movements and to prevent the abrading belt 10 from running off the reversing roller 15 and the pressing member 9, the regulating means embodying the invention are preferably constructed as shown in FIG. 5. A sensor 24, which is fastened by means of an arm to the frame 1, comprises an air supply duct 26 and an air spray 27, the air jet 29 of which is directed to an air nozzle 28. When the air jet 29 is interrupted by the presence of the edge 30 of the abrasive belt 10 a lower pressure prevails in the cavity 31 than in the case of an uninterrupted air jet 29 in the absence of the edge 30. In order to prevent an accumulation of abrasive dust in the cavity 31, the latter receives fresh air through a circulating duct 32 and a restriction 33, which is narrower than the restriction of the air spray 27.

The varying pressure in the cavity 31 is directed through a duct 34 to an upper chamber 35 of diaphragm housing 36. The chamber 37 beneath the diaphragm 38 communicates through an opening 39 in the housing 41 of a regulator and through an air exhaust 42 provided with an air filter 14, with the open air. A lever 44 is adapted to turn about a shaft 45 and is urged by a spring 46 biassed by a set screw 47 against a cam 43 connected with the diaphragm 38.

The regulator 40 comprises a compressed-air inlet 48 which communicates with a compressed-air source (not shown) through a pressure-control. The compressed air inlet is split up into two air branches 52, each communicating through a choke 49 with one of the two chambers 50 of a pneumatic motor 51 and each of which is adapted to be alternately closed and opened, respectively, by a flap 53a or 53b actuated by the sensor 24. The air branches 52 each have an air outlet 54 opening into the housing 41, the valve seat 55 of said outlets being adapted to co-operate with valves 53 formed by a rubber element 56 disposed in a set screw 57 screwed into the lever 44.

In the position of the lever 44 shown in FIG. 5, which is obtained in the presence of the edge 30, air flows through the opened flap 53a from the motor hood 50a, whereas in the closed position of the flap 53b the air pressure in the motor chamber 50b increases so that the piston rod moves in the direction of the arrow 80. In the absence of the edge 30 the lever 44 passes over to the other position, the piston rod moving in a direction opposite the arrow 80.

The cylinder 59 of the pneumatic motor 51 extends parallel to the reversing roller 15 and is adapted to pivot about a vertical center line 58 and is connected with the frame 1. The piston rod 60 is pivoted by means of a bolt 61 to a coupling element 62, which is adapted to turn about a vertical center line 63 with respect to the frame 1 and which has a radial slot 64 which slidingly engages with a vertical pin 65 connected with the auxiliary frame 13.

In this way the auxiliary frame 13 is coupled by means of the pneumatic motor 51 with the frame 1. The pin 65, which allows a vertical displacement of the auxiliary frame 13, is connected with the auxiliary frame 13 by means of a bolt 83 with a cup spring 69 and it is displaceable in a horizontal direction because it is adapted to turn about an eccentric shaft 66 after a safety screw 84 is loosened. The safety screw 84 serves as a lever for such a displacement of the pin 65 that the auxiliary frame 13 and hence the abrading belt 10 oscillate symmetrically about a central position. Each of the chambers 50 of the double-action pneumatic motor 51 comprises a spring as a buffer for the operation of the motor 51, the spring being formed by a rubber ring 68 having a length equal to that of the motor chamber 50,

but having a diameter materially smaller than that of the motor chamber 50. The lid 81 of the cylinder can be screwed by means of a pin key fitting in the bores 82 to a greater or lesser extent in the cylinder 59 in order to adjust the minimum stroke of the pneumatic motor 51 with a stable, scarcely perceptible oscillatory movement of the abrading belt 10. In dependence upon the required oscillatory stroke of the auxiliary frame 13 the pressure adjusted by the pressure-control (not shown) is increased or decreased to an extent such that the compression of the rings 68 and hence the oscillatory stroke is increased or decreased respectively.

Instead of using the lid 81, the stroke of the piston rod 60 may be adjusted by replacing each of the rubber rings 68 by different rubber rings 68 having a different length or by arranging on each side of the piston a spacer ring on the rubber ring 68.

FIG. 6 illustrates that, though not preferably, the pneumatic motor 70 may be single-acting so that only one motor chamber 71 communicates with a duct 72 of a compressed-air source through a choke 73 of the regulator 74 and with an air exhaust 75. The air exhaust 75 alternately closed and opened by a flap 76 actuated by a sensor 24, since the flap 76 is connected with the diaphragm 38 and is lifted by a compression spring 77 each time the pressure in the upper chamber 35 drops down. A compression spring 78 resets the piston 79 of the pnaumatic motor 70 in order to obtain an oscillatory movement of the auxiliary frame 13 in the variant of the regulator shown in FIG. 6.

What is claimed is:

1. An abrading machine for abrading work pieces comprising at least one frame, a guide table connected with said frame for guiding the work pieces to be abrased, a pressing member having an endless abrading belt associated therewith, said pressing member urging said belt against the work pieces, an auxiliary frame disposed adjacent the pressing member, a reversing roller rotatably journalled in said auxiliary frame and pivotable relative to said frame about a pivotal axis transverse of the rotary axis of the reversing roller a pneumatic motor for performing an oscillatory movement about the pivotal axis, said pneumatic motor coupling the reversing roller to said auxiliary frame a pneumatic sensor for detecting the presence or absence of the edge of the abrading belt, said pneumatic sensor including a sensoractuated regulating device for controlling the pneumatic motor, said pneumatic motor having at least one motor chamber which communicates through the sensor-actuated regulating device with a compressed-air source and with an air exhaust, characterized in that the sensor-actuated regulating device is provided with a choke and a sensor activated flap, the motor chamber of the pneumatic motor communicating with the compressed-air source through said choke and with said air exhaust which is alternately closed and opened by said sensor-activated flap of the regulating device.

2. An abrading machine as claimed in claim 1, characterized in that the pneumatic motor has two motor chambers and the sensor-actuated regulating device communicates with the compressed-air source, said compressed-air source being provided with two air branches, each of said branches communicating through said choke with one of said motor chambers of the pneumatic motor, each of said air branches being acterized in that a vertical pin is connected with the auxiliary frame by a coupling element which is adapted to pivot about a vertical pivotal axis, said pneumatic motor being arranged parallel to the reversing roller and engaging said vertical pin.

5. An abrading machine as claimed in claim 1, wherein the auxiliary frame is disposed above the pressing member. 

1. An abrading machine for abrading work pieces comprising at least one frame, a guide table connected with said frame for guiding the work pieces to be abrased, a pressing member having an endless abrading belt associated therewith, said pressing member urging said belt against the work pieces, an auxiliary frame disposed adjacent the pressing member, a reversing roller rotatably journalled in said auxiliary frame and pivotable relative to said frame about a pivotal axis transverse of the rotary axis of the reversing roller a pneumatic motor for performing an oscillatory movement about the pivotal axis, said pneumatic motor coupling the reversing roller to said auxiliary frame a pneumatic sensor for detecting the presence or absence of the edge of the abrading belt, said pneumatic sensor including a sensoractuated regulating device for controlling the pneumatic motor, said pneumatic motor having at least one motor chamber which communicates through the sensor-actuated regulating device with a compressed-air source and with an air exhaust, characterized in that the sensor-actuated regulating device is provided with a choke and a sensor activated flap, the motor chamber of the pneumatic motor communicating with the compressedair source through said choke and with said air exhaust which is alternately closed and opened by said sensor-activated flap of the regulating device.
 2. An abrading machine as claimed in claim 1, characterized in that the pneumatic motor has two motor chambers and the sensor-actuated regulating device communicates with the compressed-air source, said compressed-air source being provided with two air branches, each of said branches communicating through said choke with one of said motor chambers of the pneumatic motor, each of said air branches being alternately closed and opened, respectively by the sensor-actuated flap.
 3. An abrading machine as claimed in claim 1, characterized in that at least one chamber of the pneumatic motor contains a spring and a pressure-control means is included in the compressed-air supply, so that the stroke of the pneumatic motor is adjustable by said pressure control means.
 4. An abrading machine as claimed in claim 1, characterized in that a vertical pin is connected with the auxiliary frame by a coupling element which is adapted to pivot about a vertical pivotal axis, said pneumatic motor being arranged parallel to the reversing roller and engaging said vertical pin.
 5. An abrading machine as claimed in claim 1, wherein the auxiliary frame is disposed above the pressing member. 